There are, of course, many ways of finishing the exteriors of commercial and industrial buildings. One type of external wall system utilizes individual prefabricated panels that are suitably fastened to the building framing, ordinarily by a relatively light-weight retaining system to which the panels can readily be attached and by which the panels are joined to the main building framing. Within this general type of exterior panel wall system are some commercially available versions that utilize composite panels composed of thin aluminum sheets laminated to a plastic core. These composite panels fit into a frame work made up of retainers having grooves that receive the edges of the panels.
These previously known panel systems based on aluminum/plastic/aluminum composite panels have several disadvantages. For one thing, the framing system ordinarily requires that the panels and retainers be installed in step, panel by panel and retainer by retainer, working horizontally and vertically, inasmuch as the system depends upon reception of the panel edges in channels or tracks of the retainers. Thus, after a panel is installed, the retainer tracks for the then free edges of the panel are installed and so forth. As far as installation costs are concerned, the assembly procedure is relatively inexpensive and can be accomplished relatively quickly. On the other hand, there is a distinct disadvantage that any panels that might be damaged during the life of the building are difficult to replace. Moreover, the composite panels have shown a tendency to delaminate because of deterioration of the adhesives due to the effect of moisture that attacks the edges where they fit into the retainers.
Several years ago, Construction Specialties, Inc. the assignee of the present invention, developed and commercialized a panel wall system under the trademark "Tech Wall.RTM." that has numerous advantages. While there are now several versions of the "Tech Wall.RTM." panel wall system, they share the common concept of fastening shallow pan-like panels to horizontal and vertical retainers. Reference may be made to U.S. Pat. Nos. 4,622,794 (Goertner, Nov. 18, 1986) 4,506,484 (Bartlett et al., Mar. 26, 1985), 4,597,235 (Olsen, July 1, 1986) and 4,607,471 (Olsen, Aug. 26, 1986) for detailed descriptions and illustrations of the previously known (and "prior art") "Tech Wall.RTM." panel wall systems.
Among the advantages of the "Tech Wall.RTM." systems are a high degree of design flexibility in the architectural uses, a variety of joint systems, the durability of the panels, and the ability to replace damaged panels by removing only the damaged one or small groups of panels including the damaged one. The system of the Goertner patent, for example, uses T-shaped clips that fit into slots in the panel flanges to fasten the panels individually to the framing system and an adhesive sealant to seal all joints. The Bartlett et al. patent and the Olsen '235 patent describe and show arrangements of water control troughs and channels for trapping any water that intrudes through the seals (which is not unexpected after numerous thermal cycles) or that condenses behind the panels and directing it outside. The Olsen '471 patent discloses a relatively simple, low-cost version designed for use with the "rain screen" principle of curtain wall design, in which an exterior back-up sheathing wall is well-sealed, the curtain wall is designed to minimize but not always stop water intrusion, and the space between the sheathing wall and curtain wall is drained and well-ventilated to the outside to provide pressure equalization across the curtain wall. The pressure equalization limits water intrusion into the air space between the sheathing wall and curtain wall.